A sixth soldier, based in Vilseck, Germany, was identified as Staff Sgt. Jesse L. Williams, 30, of Elkhart, Ind.

Fort Riley confirmed that a seventh soldier was injured in the crash, although officials there said they could not release a name because of privacy reasons. Military officials said the cause of the crash remained under investigation.

Maj. Gen. Paul Funk II, commanding general of the 1st Infantry Division and Fort Riley, offered condolences to the soldiers’ families and friends.

"We stand ready to support them and I urge our community and the nation, while remembering their sacrifices this holiday season, to do the same," Funk said in a statement.

The deputy governor of southern Zabul province said Wednesday that a NATO helicopter crashed in the remote district of Shajau and U.S. officials later confirmed that Zabul was the location of the U.S. crash.

"The loss of six U.S. troops in a helicopter crash on Tuesday is a heartbreaking reminder of the sacrifices" the men and women serving in Afghanistan continue to make, Defense Secretary Chuck Hagel said Thursday during a Pentagon press conference that covered a range of issues. "And our thoughts and prayers go out to their families."

The 1st Division Combat Aviation Brigade sent some 2,000 soldiers to Afghanistan in August for a nine-month deployment, replacing the 3rd Infantry Division’s Combat Aviation Brigade. According to a brigade news release in September, the soldiers are responsible for providing air support over a mountainous and desert region roughly the size of Montana.